Traditionally casing and liners have been sealed in the wellbore with cement that is pumped down internally and later displaced out the bottom of the casing or liner and into the annular space between the casing or liner and the wellbore. This procedure is expensive and requires the use of specialized equipment and specially trained personnel. The process is time consuming and the equipment takes up significant space such that in offshore platforms careful logistics are required to make room for the equipment when the cementing job is required. There are also uncertainties as to the distribution of the cement causing concerns of channeling of fluids from one zone penetrated by the casing or liner to an adjacent zone.
In the past, packers that seal tubing to casing using a ring that swells on contact with well fluids have been designed. These packers combined mechanical compression of the ring with the swelling property used to enhance the tightness of the seal. An example of such a packer is U.S. Pat. No. 4,137,970. This patent describes various polymers, gels, and gels prepared from colloidal suspensions to take the place of mechanically compressed rubber to form a chemical seal ring. In water well applications, that generally are very shallow in comparison to a typical oil or gas well, jackets using grout sandwiched between flexible sheets have been wrapped around the casing and lowered into the water in the wellbore. When the water reached the grout, the grout expanded between the flexible sheets to seal the casing. The grout design is not workable for the fluids and temperatures typically seen in oil and gas wells. Additionally, there is a need to allow sufficient time in the swelling to allow time to properly place the casing or liner before significant swelling begins.
The present invention eliminates the cementing process completely. It provides for the stands of casing or liner to be wrapped between the end connections with a rubber sleeve preferably bonded to the tubular. When the sting of casing or liner is run, the rubber slowly swells to seal around the casing or liner. Optionally, the casing or liner can be expanded with a swage to reduce the volume of the annular space around the casing or liner that the rubber sleeve would have to bridge. Optionally, a packer can be placed at the lower end of the casing or liner string and a sealing hanger can be used near the top of the casing or liner string. Different formulations for the sleeves can be used that are responsive to the presence of different fluids or that induce swelling at different rates, depending on the particulars of the installation. Those skilled in the art will further appreciate the scope of the claimed invention from a description of the preferred embodiment and the claims, which appear below.